<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>11-盒模型之margin讲解</title>
<style>
    #cont{
        width: 1000px;
        height: 600px;
        background: green;
    }

    div{
        width: 400px;
        height: 200px;
        background: blue;
        float: left;
    }

    #test{
        margin: 10px;
    }

    #test3{
        width: 1000px;
    }

</style>
</head>
<body>
    <div id="cont">
        <div id="test"></div>
        <div></div>
        <div id="test3"></div>
    </div>
</body>
</html>